Electrophoretic analysis requires the application of an electric field to a suspension of macromolecules or cells being studied. In the highly sensitive method disclosed and claimed in U.S. Pat. No. 3,984,533, assigned to the assignee hereof, which involves the Doppler shift of scattered coherent light, endosmotic flow and Joule-heating convective flow are limited by closely spacing the electrodes. When in ideal circumstances the electrode gap is only about one millimeter in width, electrode pH stability and surface stability against release of particles are of major importance particularly in terms of resolution of the laser Doppler shift spectrometer. Electrodes of conventional design and construction do not satisfy these requirements, the electrically reversible silver-silver chloride type release colloidal particles into the probed volume which interfere with light scattering measurements. Non-reversible platinum-platinum black electrodes, on the other hand, do not present the surface instability problem but lack pH stability even under symmetrical application of a square wave electrical field. This pH drift effect can be reduced but by no means eliminated through the application of a coating of protein such as bovine serum albumin and the necessity for constant monitoring of electrode performance remains.